GitHub is not accessible from git-bash

The git command on a git bash installed in Windows causes various problems.

You can use git --version to verify the git installation.

The git clone command looks like this:

 git clone https://~~
Cloning into 'source'...
fatal: enable to access 'https://~~': Failed to connect to PC port 8080: Connection refused

When I try to set up a remote repository, it looks like this:

 git remote set-url origin https://github.com/~~
fatal —No such remote 'origin'

Do you know what's wrong with connecting to GitHub?